A fuel cell has been proposed as a power source for electric vehicles and other applications. In proton exchange membrane (PEM) type fuel cells, hydrogen or another suitable fuel is supplied to an anode of the fuel cell and oxygen is supplied as an oxidant to a cathode. An electrochemical reaction within the fuel cell generates electricity. A plurality of fuel cells is stacked together in a fuel cell stack. A fuel cell system includes at least one fuel cell stack and a plurality of components necessary for operation of the fuel cell stack. Typically, at least one fuel cell stack is required to power a vehicle. Large amounts of hydrogen or other suitable fuel stored in a fuel tank on the vehicle are supplied to the fuel cell stack.
The fuel tank typically stores the fuel in a highly compressed state (up to 900 bar), to decrease a size of the tank and to increase a travel range of the vehicle. The fuel tank may include a polymeric liner to militate against fuel leaks, a composite shell to withhold a pressure of the tank, and an outer casing to militate against damage to the tank. A layering of a plurality of the fuel tank components may require a biasing force from within the tank to militate against a deformation of the polymeric liner. The biasing force may be a minimum tank pressure, which must be monitored accurately when the pressure of the fuel tank is lowered. The pressure of the fuel tank may be lowered during one of an operation of the fuel cell system and in an anticipation of the fuel tank removal. A refueling of the fuel tank also requires accurate pressure monitoring. During the refueling of the fuel tank, a maximum tank pressure is monitored to militate against an overpressure of the fuel tank.
A pressure sensor affixed to one of the fuel tank and the fuel cell system is used to monitor the pressure of the tank. A cost of the pressure sensor is determined by a sensor resolution and a pressure range of the pressure sensor. The pressure sensor having a high sensor resolution (1% of a range of the sensor) and a large pressure range (from 5 to 900 bar) is excessive in cost, and increases a cost of the vehicle in which the pressure sensor is incorporated. The pressure sensor having the high sensor resolution is necessary for one of the refueling of the fuel tank (maximum tank pressure) and the anticipation of the fuel tank removal (minimum tank pressure).
For fuel cell applications, the high sensor resolution is not needed for a large portion of the pressure range (about 25 bar to 500 bar) because the maximum tank pressure and the minimum tank pressure are not reached. Accordingly, the high sensor resolution in this range is not needed and unnecessarily increases the cost of the vehicle in which the pressure sensor is incorporated.
There is a continuing need for a pressure sensor that is cost-effective, has a large pressure range, and has a high relative accuracy in a low pressure range and a high pressure range.